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The Accreting Neutron Star GX 301-2 with NICER

Published onJun 01, 2020
The Accreting Neutron Star GX 301-2 with NICER

The accretion-powered high-mass X-ray binary GX 301-2 is composed of a neutron star accreting from a B1-type stellar companion. Discovered more than fifty years ago, it is one of the brightest X-ray sources in the sky. Its lightcurve is modulated by the ~41-day orbital period of the system, with X-ray emission consistent with accretion from the strong wind of the stellar companion onto the pulsar. In early 2019, GX 301-2 had a spin-up episode lasting two orbital periods in which the pulsar increased its spin frequency by 2%. In this paper, we analyze 13 observations of GX 301-2 taken with the NICER X-ray observatory between 28 Dec 2018 and 15 February 2019, totaling 29 ksec. The 2-10 keV energy spectrum is well-described by a partially-covered power law with spectral index between 0.95 and 1.42. Fluorescent line emission from Fe K-alpha and S K-alpha are clearly detected. We study the spectral and timing properties of the X-ray emission as well as the angular momentum evolution of the pulsar to place constraints on the geometry of the accreting stream.

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